Human Milk
Most persons in America eat much more protein than this. But that 10 calories out of 100 is not too small an allowance is evidenced by the analysis of human milk. The growing infant needs the maximum proportion of protein. In the dietary of the domestic animals, the infant’s food, the mother’s milk, is richer in protein than the food of the grown animal. Consequently an analysis of human mother’s milk affords a clue to the maximum protein suitable for human beings. Of this milk 7 calories out of every 100 calories are protein. If all protein were as thoroughly utilized as milk-protein or meat-protein, 7 calories out of 100 would be ample, but all vegetable proteins are not so completely available. Making proper allowance for this fact, we reach the conclusion that 10 calories out of every 100 are sufficient.
Excessive Use of High-Protein Foods
A chief and common error of diet consists, then, in using too much protein. Instead of 10 calories out of every 100, many people in America use something like 20 to 30. That is, they use more than double what is known to be ample. This excessive proportion of protein is usually due to the extensive use of meat and eggs, although precisely the same dietetic error is sometimes committed by the excessive use of other high-protein foods such as fish, shell-fish, fowl, cheese, peas and beans, or even, in exceptional cases, by the use of foods less high in protein when combined with the absence of any foods very low in protein. The idea of reducing the protein in our diet is still new to most people.
Injuries From Over-abundance of Protein
Prof. Rubner of Berlin, one of the world’s foremost students of hygiene, said, in a paper on “The Nutrition of the People,” read before the recent International Congress on Hygiene and Demography:
“It is a fact that the diet of the well-to-do is not in itself physiologically justified; it is not even healthful. For, on account of false notions of the strengthening effect of meat, too much meat is used by young and old, and by children, and this is harmful. But this meat is publicly sanctioned; it is found in all hotels; it has become international and has supplanted, almost everywhere, the characteristic local culinary art. It has also been adopted in countries where the European culinary art was unknown. Long ago the medical profession started an opposition to the exaggerated meat diet, long before the vegetarian propaganda was started. It was maintained that flour foods, vegetables, and fruits should be eaten in place of the overlarge quantities of meat.”
When protein is taken in great excess of the body’s needs, as is usually the case in the diet of Americans, added work is given the liver and kidneys, and their “factor of safety” may be exceeded.
Animal Proteins
Flesh food—fish, shell-fish, meat, fowl—when used in great abundance, are subject to additional objections. They tend to produce an excess of acids, are very prone to putrefaction, and contain “purins” which lead to the production of uric acid. This is especially true of sweetbreads, liver and kidney. The well-known deficiency in flesh foods of lime often needs to be taken into consideration in the dietary. Some of the vegetable foods, such as peas and beans, rich in protein, are likewise not free from objection. Their protein is not always easily digested and is, therefore, likewise liable to putrefaction. Unlike most vegetable foods, they contain some purins. These foods are, however, rich in iron, which renders them a more valuable source of protein for children and anemic people than meat. Also, an excess of protein is not so likely to be derived from such bulky foods as from meat, which is a concentrated form of protein.